It has been known to construct a furnace such as a pusher furnace, useful for the heat treatment of metal work pieces proceeding through the furnace, with a flue for offgases located adjacent the charge end. As the workpieces proceed through the furnace from underneath the flue, they travel through a restricted, or throat section of the furnace, to a heat chamber. At the far end of the heat chamber, the heated workpieces are discharged from the furnace.
It has been possible to construct the roof and wall sections of such furnaces of ceramic fiber to enhance the insulation characteristics of such surfaces. Typical construction for these structures has been shown for example in U.S. Pat. No. 4,411,621.
Although such furnaces can provide for economical insulation as well as efficient workpiece heat treatment, even for a somewhat varied workpiece charge rate, where a more extended variation in rate is desired, or even where product interruption can occur, such furnaces tend to be uneconomical. Although positioning a recuperator at the flue outlet will assist in initial economy of operation, recuperator maintenance can diminish overall achieved economy.
It would therefore be desirable to construct a furnace operating most efficiently not only over a wide range of workpiece throughput but also providing economy of maintenance during product interruption. It would also be desirable to construct such a furnace, e.g., a pusher furnace, that can maintain the worthwhile insulation features afforded by the use of ceramic fiber insulation.